Computation of Vibration-Dissociation Nonequilibrium Boundary Layers: Comparison of Various Models

In the inner part of the dissociated boundary layer of hypersonic bodies, a vibrational freezing zone has been observed. This freezing region takes place even if, in the outer part of the boundary layer, translation and vibration temperatures are in equilibrium and even if the surface is catalytic. This phenomenon can be attributed to the diffusion towards the wall of the vibrational energy; consequently the dissociation rate constantsin this region can increase. Advanced physical models taking into account the vibration-chemistry interaction are required for the description of such flows. State-to-state and statistical global models are described in this paper and used in the computation of hypersonic boundary layers. All methods can predict the general features of the freezing phenomenon and present a qualitative agreement, as far as similar assumptions are used. Applications to boundary layers behind a reflected shock wave and along a hemispherical body are also presented.